Abstract

Anthracnose disease is one of the major economic constraints to chilli production in tropical and subtropical regions. Ten isolates of Colletotrichum capsici causing chilli anthracnose were collected from 10 provinces in the northeast of Thailand. The isolates were evaluated for their morphological and cultural characteristics, pathogenic variability on chilli fruits and genetic characterization using random amplified polymorphic DNA (RAPD-PCR). Based on the morphological traits and cultural characteristics of the C. capsici populations, 10 isolates were categorized into six groups. These were designated, respectively, as CC-I, CC-II, CC-III, CC-IV, CC-V and CC-VI. In Potato Dextrose Agar culture, most of the isolates produced cottony colonies. However, differences were obtained in colony color, shape and size of conidia. Based on the effect of carbendazim, 10 isolates were classified into two groups designated as highly resistant group (<40% inhibition) and highly sensitive group (>90% inhibition). Three virulence degrees of 10 isolates on chilli fruits were evaluated. Molecular polymorphism generated by RAPD confirmed the variation of the different isolates and they were grouped into two clusters. However, morphological, pathological and RAPD grouping of isolates suggested no correlation among the test isolates.

Key words: Colletotrichum capsici, morphological and cultural characteristics, pathogenic variability, random amplified polymorphic DNA (RAPD).